Field of the Invention
The present invention relates to a sheet feeder that feeds a sheet to an image forming unit for forming an image on a sheet and an image forming apparatus including the sheet feeder.
Description of the Related Art
A typical image forming apparatus, such as a copier or a printer, includes an image forming unit for forming an image on a sheet, such as plain paper, coated paper, or film paper, and a sheet feeder for supplying a sheet to the image forming unit. The sheet feeder includes a sheet storage case (e.g., a sheet cassette) for storing sheets. A user places sheets for image formation in the sheet storage case and loads the sheet storage case into a main body (hereinafter, “apparatus main body”) of the image forming apparatus. A sheet feeding unit including a feed roller and a separation roller separates sheets, which are stored in the sheet storage case loaded in the apparatus main body, one by one and then feeds the separated sheet to the image forming unit.
Some image forming apparatuses are configured such that the sheet storage case is unloaded from the apparatus main body in a direction orthogonal to a sheet feeding direction in which a sheet is fed from the sheet storage case loaded in the apparatus main body. This configuration is called a front loading type in which the sheet storage case is loaded into the image forming apparatus from a front side of the apparatus, and the sheet feeding unit feeds a sheet from the loaded sheet storage case in the direction orthogonal to the direction in which the sheet storage case is loaded into the image forming apparatus.
In this configuration, a top sheet of a sheet bundle stored in the sheet storage case may abut a component, for example, the sheet feeding unit, of the apparatus main body while a user loads the sheet storage case into the apparatus main body after the user places sheets in the sheet storage case. In particular, when sheets stored in the sheet storage case correspond to a maximum loading capacity of the sheet storage case, or alternatively, when sheets are warping (curling), such a phenomenon tends to occur.
If a sheet stored in the sheet storage case abuts an internal component of the apparatus main body and is caught by the component during loading of the sheet storage case into the apparatus main body, the sheet may be damaged, for example, broken, or the orientation of the sheet may be significantly changed. The changed orientation of the sheet causes sheet misfeed (e.g., sheet jam (hereinafter, “jam”) or sheet skew feed (hereinafter, “skew feed”)) when the sheet feeding unit feeds the sheet from the sheet storage case loaded in the apparatus main body.
To prevent a sheet in the sheet storage case from being caught during loading of the sheet storage case into the apparatus main body, for example, a recently developed image forming apparatus has a configuration in which a feed roller has at one end a sheet guide surface (refer to Japanese Patent Laid-Open No. 8-290846). In this configuration, if sheets stored in the sheet storage case have curling ends, the sheets are guided by the guide surface at the end of the feed roller during loading of the sheet storage case into the apparatus main body. Consequently, the sheet storage case can be smoothly loaded into the apparatus main body without any damage to the stored sheets.
When the sheet storage case is loaded into the apparatus main body, sheets stored in the sheet storage case may be insufficiently regulated such that an end of a sheet partly projects from the sheet storage case in the sheet feeding direction. In such a state, projecting part of the sheet may abut a component other than the feed roller of the apparatus main body during loading of the sheet storage case into the apparatus main body. For example, the end of the sheet projecting from the sheet storage case may abut a conveying guide, disposed in the vicinity of the sheet feeding unit, for guiding a sheet fed by the sheet feeding unit. Disadvantageously, the sheet may be damaged or the orientation of the sheet may be significantly changed, causing sheet misfeed, such as jam or skew feed.
The above-described disadvantage, however, is not overcome by the related-art configuration in which the end of the feed roller has the sheet guide surface as described in Japanese Patent Laid-Open No. 8-290846.